Electrical etching.



J. H. WEEKS.

ELECTRICAL ETCHING. APPLICATION man MAR. a. tan.

1,2883%, Patented Dec.24,1918.

ED STATE% PATENT @FFIQE.

JOSEPH HENRY WEEKS, OF RUT EDGE, PEN SYLVANIA, ASSIGNOR TO JACKSON s. WEEKS, OE DELAWARE COUNTY, PENNSYLVANIA, AND RAYMOND M. WEEKS, 0F PHILADELPHIA, PENNSYLVANIA, TRUSTEES.

ELECTRICAL ETCHING.

Specification of Letters Patent.

Patented Dec. 24, 1918.

Original application filed April 1, 1916, Serial No. 88,362. Divided and this application filed March 3, 1917.

Serial No. 152,302.

To all tU/LOHL it may concern:

Be it known that I, JOSEPH H. WEEKS, a citizen of the United States, residing at Rutledge, in the county of Delaware, State of Pennsylvania, have invented certain new and useful Improvements in Electrical Etchings, of which the following is a specification, reference being had therein to the ac companying drawing.

My invention relates to electrical etching and has for its object the provision of an improved process of and composition for electrical etching as hereinafter described.

The present invention is a division of my prior application Serial Number 88,362,file April 1, 1916.

A suitable form of apparatus made use of in carrying out my invention is illustrated in the accompanying drawings to which reference will be had in the description in which- Figure l is a plan view of a tank with a plate suspended therein face down, and cathodes hung vertically upon wires along the sides and edges of the tank.

Fig. 2 is a longitudinal view of the same partly in section, showing the cams and slides for raising and lowering the plate in the solution while etching.

Referring to the drawings, projections 50 on the sides of the tank carry a wire or rod 51 extending around the entire upper part of the tank and having extension terminals connected to the negat ve terminal of the source of current.

My cathodes 52, consisting preferably of from a pair of rods 54., consisting of copper wire bent in a loop at each end, and connected at both ends to the positive terminal of the source of current, which is preferably a dynamo of low voltage, but maybe any convenient and suitable source.

When a large quantity of solution is em ployed, the up and down motion of the anode can be dispensed with, but I consider it very .Figs. 1 and 2.

desirable to gently move the anode at constantly recurring intervals. Mechanism for producing this motion of the plate is also provided in the form of apparatus shown in Ihere show a shaft 55 beneath the tank, with its ends journaled in bearings secured thereto, provided with a pulley 56 at one end for attachment to any suitable driving'means. Vertical slides 57 are provided on the ends of the tank which at their upper ends carry the wires or rods 54 and at their lower ends are slotted to slide up and down on the shaft, with roller bearings 58 resting upon the surface of rotary cams 59 on the shaft. As the shaft rotates, the cams 59 raise and lower the rollers 58 and the slides 57 to which they are attached, thereby raising and lowering the wires 54, which play between guides 60 in the top of the tank.

In order to lessen the quantity of solution required in the tank, and also to draw the heavy solution flowing from the anode plate directly to the base of the cathode or cathodes, I- insert a filler or block shown in Figs. 1 and 2. This is geometrically shaped, preferably with triangular ends, sloping sides, and its longitudinal ridge lying directly under the anode plate. It is made of acid resistant material or wood or metal,

coated with the same and water-tight. This filler is shown at 61, in dotted lines, in Figs. 1 and 2. I

I consider it novel and original with me to arrange the'cathodes in the manner shown and described in the several figures so. as-to permit an even distribution of the current in all parts of the bath. I have hitherto worked upon the generally accepted theory that theanode and cathode must face each other in parallelism so that the passage of current from one to the other through the bath should be in lines as nearly normal to both surfaces as possible; but experience has shown me that this is unnecessary, provided that the points of sufiicient surface and even distribution of current are taken care of.

For the solution or electrolyte in the tank, I prefer certain formulas of my own, which I shall now state.

Solution No. 1: Dissolve ammonium chlorid in water until the solution registers from 5 (with heavy Baum hydrometer) to to be done.

a point of almost saturation. This solution can be used alone, but preferably I add an acid which may be nitric, hydrochloric, chromic, citric, or acetic. ()ther acids may be employed if desired. The proportion of acid as well asthe strength of ammonium chlorid vary with the character of the work It is obvious that with the stronger acids, a smaller quantity thereof is required; and the stronger the annnoniuln chlorid solution the larger the amount of acid which may be employed. These acids increase the conductivity of the solution, which also varies with the strength of the chlorid solution. The acids also serve to keep the face of the anode clean and bright.

No. 2. Ammonium chlorid in water to Baum test 20 1 gal. Sulfuric acid 1 oz.

Having thus described the apparatus and composition of the electrolysis, I shall now proceed with the steps in the operation. The first step consists in producing the image on the plate by any of the photographic or transfer methods well known in the graphic arts. I I

The back of the plate is next coated with an insulating material, which may be chosen from a great variety, such as shellac dissolved in alcohol, a solution of asphaltum and paraflin, or almost any waxous sub stance, to Which has been added a resin or asphaltum, or both.

The plateis then connected with the positive wire of a dynamo or battery and immersed in a suitable electrolyte, constituting the anode terminal therein. I have found it preferable in electrical etching to maintain the plate horizontally in the electrolyte with the face (the .side containingthe image) downward, as hereinbefore de- 4 scribed.

In line plates or what is known as line portions of combination plates, after a certain depth is attained, which is technically termed (in chemical etching), the first of the lines after having obtained a certain depth, reinforcing the side of the lines must be done in four directions, whether the plate be etched electrically or chemically, and this I must therefore do in my electrical etching method, although I am able to obtain a greater depth before this becomes necessary than is possible in chemical etching. It may readily be seen that in very small spaces,

such as between lines that are approximately one fiftieth of an inch apart, the powder en-' tirely fills the opening and this receives no further etching after the first etching, so that the depth of the plate in such fine portions, therefore, depends entirely upon the first etching.

After powdering more or less of a shoul der is produced, hence by getting my plate so much deeper in the first etching, the possibility of shoulders on the sides of the lines near the printing surface is entirely obviated. Shoulders it may be added, increase the difficulty of printing any plate.

Having thus described my invention what 1 claim and desire to secure by Letters Patcut is:

In electrolytic etching, an anode carrying a resistant image to be etched in combination with an electrolyte consisting of a solution of chlorid of ammonium with the addition of an acid.

In testimony whereof I affix my signature.

JOSEPH HENRY WEEKS. 

